body {
    font-family: 'Segoe UI', sans-serif;
    margin: 0;
    background: #f3f9ff;
  }
  
  nav {
    background: #ffffff;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    padding: 1rem 2rem;
    position: sticky;
    top: 0;
    z-index: 100;
  }
  
  .nav-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
  }
  
  .logo {
    font-size: 1.3rem;
    font-weight: bold;
    color: #003366;
  }
  
  .nav-links a {
    margin-left: 1rem;
    text-decoration: none;
    color: #444;
    font-weight: 500;
  }
  
  .container {
    max-width: 800px;
    margin: 2rem auto;
    padding: 1rem;
    text-align: center;
  }
  
  h1 {
    font-size: 2.2rem;
    color: #1a202c;
    margin-bottom: 1rem;
  }
  
  p {
    font-size: 1.1rem;
    color: #333;
  }
  
  .btn {
    padding: 0.8rem 1.5rem;
    margin: 1rem;
    border-radius: 8px;
    color: white;
    font-weight: bold;
    text-decoration: none;
    display: inline-block;
  }
  
  .btn.blue {
    background-color: #007bff;
  }
  
  .btn.green {
    background-color: #28a745;
  }
  
  .theme {
    margin-top: 2rem;
    font-style: italic;
    color: #555;
  }
  .nav-links a.active {
    color: #2563eb;
    font-weight: bold;
    border-bottom: 2px solid #2563eb;
    padding-bottom: 2px;
  }
  
  .btn {
    padding: 0.8rem 1.5rem;
    border-radius: 8px;
    font-weight: bold;
    text-decoration: none;
    color: white;
    transition: background-color 0.2s ease;
  }
  
  .btn.blue {
    background-color: #2563eb;
  }
  .btn.blue:hover {
    background-color: #1d4ed8;
  }